bluedun

1996 Civic DX with 65K. History is at 25K, engine rpms were fluctuating when warm, surging in neutral, ran fine cold. Code was P0505 so the idle control vale was replaced, been fine for 40K miles. Now the check engine light came on and the idle dropped slightly with slight roughness. DTC code is P0505 again , idle control circuit. Replaced the idle control valve, cleared the code. Started the car, check engine light came right back on but idle and driving seem ok. Any ideas what to check now? Thanks!

crazyhorse2011

Unplug the battery for 10 minutes, making sure to flip your headlight switch on and off a couple times with the battery unplugged to discharge any static buildup. Plug battery back in and start car and drive around for 5 minutes or whatever, if the code doesnt come back your good if it comes back see what it is.

bluedun

The battery was unplugged while I changed the idle control valve but I didn't flip the headlight. I will try it. The old idle control valve looked pretty clean btw so I was suspicious it might not be the reason for the code. Also contrary to what I found online and in the service manual, the valve can be changed (four 8mm bolts , two coolant lines and the electrical plug) without removing a downdraft throttle body. You just have to move the throttle cable bracket (only 2 bolts on the manifold) to make it easier to get to the 2 lower 8mm bolts. Easy job really..

crazyhorse2011

yeah ive never done it on the 96-00 civics. did it on my 95 and it sits easily behind the throttle body and with a wrench you can crack the 3 10mm bolts and pull it off.

ok so your saying you already had the battery undone. now get in the car and get that engine code and tell us what it is.

bluedun

ok, reset it again. started car, check engine light lit up in a few seconds. code 14 came back after a 5 m in drive. P0505, idle air control.
you wouldn't know anything was wrong if the light wasn't on. thanks for the help.

crazyhorse2011

There could be a problem with the wiring to the sensor. Im not too knowledgeable on how to test that though.

the only other thing i could think of is to make sure the plug isnt damaged and the metal contacts on the iacv are damaged either. Otherwise im stumped. If you have 2 known good iacvs and they both throw CEL it has to be wiring or ecu. Maybe try a different ecu and see if it gets the code too